Amid tensions in the contested South China Sea, the navies of the United States and the 10 ASEAN member-states will stage their first combined maritime exercise in early September in the Gulf of Thailand, the Thai Navy announced Friday.

The five-day drills consisting of at least eight ships and two aircraft will kick off from the Sattahip Navy Base in Thailand's Chonburi province on Sept. 2 and conclude on Sept. 6, according to a statement released by the Thai Navy.

Thai Rear Admiral Sompong Nakthong and Capt. Matt Jerbi, commodore of Destroyer Squadron 7 with the U.S. Navy's Seventh Fleet, will lead the drills, the statement said.

The drills involving the United States and navies from the Association of Southeast Asian Nations will be "the first multilateral maritime exercise between the navies of the ASEAN countries and the U.S. Navy," it said.

"It focuses on prevention and suppression of illegal activities in the seas. Members will share information, build awareness and co-operate under the international law and each individual country's law," the statement added.

The drills will extend from Chonburi to the tip of Ca Mau, Vietnam's southernmost province, Kyodo News reported.

Vietnam and three other ASEAN countries - the Philippines, Malaysia and Brunei - along with Taiwan and China have territorial claims in the South China Sea, where tensions have been high lately over Chinese maritime activities. Beijing claims nearly all of the sea, including areas close to its neighbors.

In June, officials in Manila voiced anger after a Chinese trawler struck and sank an anchored Philippine fishing boat in waters claimed by the Philippines.

Officials from the United States, meanwhile, have accused Beijing of "its bullying behavior" in the sea region.

On Thursday, the U.S. State Department said Washington was deeply concerned about a series of "aggressive steps" by China in recent weeks, including Beijing's alleged interference with Hanoi's oil and gas activities in Vietnam's Exclusive Economic Zone in the sea.

The State Department cited China's redeployment of a government-owned survey vessel, together with armed escorts, into waters offshore Vietnam near Vanguard Bank on Aug. 13 as an "escalation by Beijing in its efforts to intimidate other claimants out of developing resources in the South China Sea."

The coordinated drills by the U.S. and ASEAN navies will take place in the Gulf of Thailand nearly a year after ASEAN and China staged their first joint naval exercise off Zhanjiang, in Guangdong province, in October 2018.

On Friday, spokespersons for the U.S. Department of Defense in Washington and the U.S. Indo-Pacific Command in Honolulu did not immediately respond to emails from BenarNews, an RFA-affiliated online news service, seeking more information about the upcoming drills in the Gulf of Thailand.

In Hanoi on Friday, Vietnam's Prime Minister Nguyen Xuan Phuc expressed "deep concern" about the recent developments in the South China Sea.

The first public official statement from the head of the Vietnamese government on the South China Sea after the Chinese fleet of oil exploration ships entered the exclusive economic zone and continental shelf of Vietnam for the second time came during a news conference with Australian Prime Minister Scott Morrison in Hanoi.

In what Australian media said was a thinly veiled swipe at Beijing's aggression in the South China Sea, stressed the importance of an "open, inclusive and prosperous Indo-Pacific neighborhood".

"An Indo-Pacific where we respect each other's sovereignty and independence, because if we allow the sovereignty or independence of any of our neighbors to suffer coercion, then we are all diminished," he said.

In Washington on Friday, about 100 Vietnamese-Americans staged a protest at the Chinese embassy, calling for and end to Chinese incursions at Vanguard Bank and in Vietnam's EEZ.

Reported by BenarNews, an RFA-affiliated online news service, and by RFA's Vietnamese Service.